Existing band type sawmills typically have wheel bearing mounts that are tilted or revolved about an eccentric shaft to tighten the band saw blade. As the bearing mounts move in a nonlinear direction to tighten the blade, the blade can become out of parallel with the log supporting table. In addition, when the bearing mount is repositioned by a threaded adjustment mechanism or a hydraulic cylinder, the wheel bearings become unyielding to fluctuating loads exerted against the blade. Designs such as these in current sawmills can reduce blade life and cause undesirable variations in board thickness.
Some sawmills may only have a log supporting table that is adjustable. Others have a stationary table with only the height of the band saw being adjustable. With either design, however, the ability to effectively clamp logs of various diameter is limited.
In addition, many sawmills are designed to cut boards to only a single thickness.
To avoid the limitations and problems of current sawmills, it is an object of the subject invention to provide a sawmill having both an adjustable height band saw trolley and an adjustable log supporting table to accommodate logs of various diameter.
Another object of the invention is to provide a means for maintaining constant blade strain regardless of variations in blade circumference and band saw wheel spacing.
Another object is to provide a direct acting blade strain device that urges the blade wheels apart in a linear direction, without any intermediate linkage.
Yet another object is to provide a blade strain device that is so compact that it fully fits directly between the blade supporting wheels.
Still another object of the invention is to provide a blade strain device incorporating a hermetically sealed bellows instead of a cylinder to minimize the number of sliding parts that could be susceptible to saw dust contamination.
Yet still another object of the invention is to provide a gas charged blade strain device that is readily separated from its high pressure supply, facilitating its use on a moveable trolley.
A further object is to provide a set works having a single detent bar and a single limit switch, yet being readily indexable to cut boards of eight different thicknesses.
Still yet another object is to incorporate a table position indicator into a sawmill having both an adjustable table and adjustable trolley rails. This enables an operator to readily position the table just prior to the last series of cuts such that the last cut leaves a standard sized board. Previous, more complicated methods require knowing the remaining log thickness and subtracting the cummulative thickness of the boards to be cut plus the width of each cut.
These and other objects will be apparent from the attached drawings and the description of the preferred embodiment that follow below.